NEW HAVEN -- Despite some triumphs reining in nitrogen and other environmentally harmful substances entering Long Island Sound, Gov. Dannel P. Malloy and others said maintaining that progress will rely on efforts to address the complex consequences that global warming will have on preservation efforts.

Esty said, however, that overall conditions are also affected by sewage treatment plants in New York that are not as modernized, an effort that will require billions in investment.

"They need to invest and the level of federal support is not making that any easier," he said.

Officials expressed measured optimism about ongoing sewage plant modernizations and a general trend towards reduced nitrogen levels and better conditions for aquatic life, though are sobered by a continued die-off of lobsters and uncertainty about how climate change and associated factors such as sea level rise and fiercer storms will affect life in the state.

Lieberman, who is not running for re-election, said governmental efforts to grapple with hypoxic conditions in the Sound, along with greater environmental stewardship, has resulted in proactive efforts to curb the flow of sewage discharged from boats and fix outmoded plants that helped nurture hypoxia, the condition when low dissolved oxygen levels in water makes it uninhabitable for marine life.

"There was a time when we were acting as if we could do anything to the Sound and put anything in it and it could still remain as pure and beautiful as it was," he said.

Lieberman noted that even with vigilant efforts from private citizens along with state, local, and federal support, other states need to be committed to helping protect the resource for it to remain an ecologically vibrant estuary.

Of particular concern is the continued decimation of the state's lobster fishery, particularly in the western end of Long Island Sound, he said.

Warmer temperatures have also brought in new species of fish that will change the Sound's ecology, Lieberman said.

"We have reason to feel proud, but the lesson is, there is no rest for those seeking to protect this water body and make sure it remains as good as it can be," Lieberman said. "Unless we help the Sound it will not survive."

State Rep. Terry Backer, who has prominently supported efforts to explore the causes of an ongoing lobster die-off, said the next phase of preservation efforts will require exploiting available technologies for reducing polluted run off and update bans on environmentally harmful substances.

"The fact that we continue to find the public will and political will is a testament to the importance of this body of water," Backer said.

Blumenthal said environmental organizations along with the state's Congressional delegation also need to remain engaged to stop periodic proposals for industrial use of Long Island Sound that are environmentally harmful, including placing of underwater power cables through the water body.

Blumenthal is opposed to a possible sale of the federally owned Plum Island, an 840-acre island off eastern Long Island that could be developed into housing or kept as a nature preserve.

"It's very definitely a threat, partly because it is a unique and significant opportunity for use by residents of both Connecticut and New York for recreation and enjoyment but also because it is such a profoundly important habitat for birds and other habitat," he said.

Blumenthal said the continued decimation of the lobster population, whether due to warmer water, pesticides or chemicals in stormwater runoff, or a combination of factors, needs further research to understand and attempt to foresee how the Sound's ecology is changing.

"The lobsters are maybe a warning about something that is happening in the Sound which is very dire and dangerous whether they are dying off from water temperatures, pesticides or some other phenomenon," Blumenthal said. "It is one down note among several that need serious attention, including climate disruption, the potential impacts of fertilizer or pesticide run off, and the quality of the watershed that feeds the Sound."